The long-range objective of this research is to establish broad range, accurate, and reliable theories about phonation that can be useful in establishing refined and applicable concepts and approaches for helping people with voice problems. This goal, of necessity, must develop, use, and refine widely effective models of phonation, and quantify the biomechanical, aerodynamic, and acoustic factors that control laryngeal function and voice quality. The objective of this application is to establish a firm understanding of the biomechanics, kinematics, aerodynamics, and acoustics of vocal fold oscillation, hemilarynx phonation, register shift, and vocal fold impact dynamics. This objective will be met through a unique combination of experimental and computational methods. In this research, an innovative combination of three complimentary models will be used. The three models are: excised larynx model, a mechanical larynx model, and a finite-element biophysical model. The results of this work will not only enhance our understanding of normal phonation, but will elucidate how vocal lesions develop and how disorders such as vocal fold paralysis disrupt vocal fold vibration, which in turn could provide insight into improved surgical and behavioral treatment of voice disorders. The specific aims for this funding period are: (1) To establish the control mechanisms for decoupling vocal fold oscillation; (2) To establish optimal conditions for hemilarynx oscillation; (3) To establish the control mechanisms for transition between chest and falsetto registers; and (4) To establish the biomechanical and aerodynamic factors that influence the potentially damaging dynamic pressures and internal and external tissue stresses. The outcome of this research project should provide significant guidance and understanding of important issues in phonation, namely, the control of vocal fold oscillation, hemilarynx phonation, register transition, and potentially damaging impact forces on the vocal fold. [unreadable] [unreadable]